1. Field of Invention
This invention relates in general to a transistor component of an integrated circuit, and more particularly to a type of high density transistor component and its manufacturing method.
2. Description of Related Art
Most metal-oxide-semiconductor (MOS) transistors consists of a gate oxide layer, a gate terminal and ion implanted source/drain regions. In order to increase the level of integration for integrated circuits so as to attain the sub-micron manufacturing realm, the component dimensions and hence the transistor channel length has to be reduced, thereby generating undesirable short channel effects. Furthermore, when the transistor channel length is reduced, as a result of an increase in the horizontal electric filed inside the channel, the electrons in the channel near the drain end will be greatly accelerated by the high electric field there to an energy level beyond normal thermal equilibrium, thereby producing numerous hot electrons. Carrier multiplication caused by the bombardment by these hot electrons will damage the gate oxide layer leaving a trail of electrons trapped inside the gate terminal, which will lead to component ageing and related reliability deterioration resulting in electron punch through phenomenon.
For a better understanding of the electron punch through phenomenon, refer to FIG. 1. FIG. 1 shows a cross-sectional view of a conventional lightly doped drain (LDD) transistor component. The lightly doped drain transistor component is formed by defining a component region above a silicon substrate 10 followed by forming a gate oxide layer 11, a gate terminal 12 and spacers 14 above the component region. Then, two ion implantations are performed utilizing the spacers 14 to form the lightly doped source/drain regions 13 and the heavily doped source/drain regions 15 respectively. However, this type of conventional manufacturing method can no longer reduce the overall channel length any further, and therefore it is difficult using this conventional method to further increase the density of integrated circuits. It is therefore an object of this invention to provide our improved transistor component with respect to areas such as short channel effects, hot electron effects and the reduction of the channel length, thereby producing high density integrated circuits as well as lowering manufacturing cost.